Bicycle control device, motor assist bicycle including bicycle control device, and method of controlling motor of motor assist bicycle

ABSTRACT

A bicycle control device controls a motor to assist driving of a wheel of a bicycle. The bicycle control device includes a controller configured to control the motor and an operation unit configured to be operated to switch operation modes of the motor. The controller includes at least a walk mode as the operation modes. In a case that a rotation speed of a wheel becomes lower than or equal to a predetermined value while the motor is driven in the walk mode, the controller is configured to control the motor so as to gradually decrease output of the motor and then stop driving the motor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2014-146950, filed on Jul. 17,2014, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a bicycle control device, a motorassist bicycle including a bicycle control device, and a method ofcontrolling a motor of a motor assist bicycle.

BACKGROUND ART

Japanese Laid-Open Patent Publication No. 2012-144061 discloses a motorassist bicycle that drives a motor to assist driving of a wheel whenpushing and walking the bicycle in addition to when riding the bicycle.The motor assist bicycle includes a walk switch. When the walk switch ispushed, a control device of the motor assist bicycle determines whetheror not the rider is walking the bicycle from the depression forceapplied to the pedals and the rotation speed of the crankshaft. When thecontrol device determines that the rider is walking the bicycle, thecontrol device drives the motor in a predetermined drive mode, namely, awalk mode. The walk switch is also used as a switch that adjusts assistdrive force during normal riding.

When the rider operates the switch during normal riding to adjust theauxiliary drive force, the motor may be driven in the walk mode eventhough the rider does not intend to do so.

SUMMARY

One aspect of the present disclosure is a bicycle control device thatcontrols a motor to assist driving of a wheel of a bicycle. The bicyclecontrol device includes an input unit and a controller configured toswitch, when the input unit is operated, between a ride mode thatcontrols the motor in correspondence with manual driving force and awalk mode that drives the motor in correspondence with the operation ofthe input unit. After switching to the walk mode, the controller isconfigured to drive the motor in correspondence with the operation ofthe input unit.

A further aspect of the present disclosure is a method of controlling amotor that assists driving of a wheel of a bicycle. The method includes,by a bicycle control device, switching, when an input unit is operated,between a ride mode that controls the motor in correspondence withdriving force and a walk mode that drives the motor in correspondencewith the operation of the input unit; and driving the motor inaccordance with the operation of the input unit after switching to thewalk mode.

Other aspects and advantages of the present disclosure will becomeapparent from the following description, taken in conjunction with theaccompanying drawings, illustrating by way of example the principles ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best beunderstood by reference to the following description of the presentlypreferred embodiments together with the accompanying drawings in which:

FIG. 1 is a schematic diagram of a motor assist bicycle;

FIG. 2 is a block diagram of a bicycle control device;

FIG. 3 is a schematic diagram of an operation unit and a display;

FIGS. 4 and 5 is a flowchart illustrating the processing of modeswitching;

FIG. 6 is a flowchart illustrating the processing of mode switching in amodified example;

FIG. 7 is a schematic diagram of an operation unit and a display in amodified example;

FIG. 8 is a waveform chart of a torque command value that corresponds tothe operation of a walk switch; and

FIG. 9 is a waveform chart of a torque command value when forciblystopping the motor while walking the bicycle.

DESCRIPTION OF EMBODIMENTS First Embodiment

A bicycle control device will now be described with reference to FIGS. 1to 5.

In the description hereafter, the left side refers to the left side asviewed from a rider, who is riding a motor assist bicycle, and the rightside refers to the right side as viewed from the rider on the bicycle.The front side refers to the front of the bicycle, and the rear siderefers to the rear of the bicycle.

FIG. 1 shows one example of a motor assist bicycle including a bicyclecontrol device.

The motor assist bicycle includes a frame 2, two rotatable wheels (frontwheel 4 and rear wheel 6) coupled to the frame 2, a drive mechanism 8that drives the rear wheel 6, a handle 10 that turns the front wheel 4,a saddle 12, a battery 14, an operation unit 16, and a display 18.

The operation unit 16 and the display 18 are attached to, for example,the handle 10.

The battery 14 is coupled to, for example, the frame 2 or a rearcarrier. Alternatively, the battery 14 may be coupled to both of theframe 2 and the rear carrier. The battery 14 supplies the drivemechanism 8 with electric power.

The drive mechanism 8 includes a crank unit 20, a chain 22 thattransmits power from the crank unit 20, and a rear sprocket 24 rotatablewith respect to the axle of the rear wheel 6 and coupled to the rearwheel 6 and driven by the chain 22. The crank unit 20 includes acrankshaft 26, a front sprocket 28 that transmits rotational force fromthe crankshaft 26 to the chain 22, and a motor 30 that assists thedriving of the rear wheel 6.

A one-way clutch transmits rotational force from the crankshaft 26 tothe front sprocket 28. When the crankshaft 26 is rotated in the forwarddirection, the one-way clutch transmits rotational force from thecrankshaft 26 to the front sprocket 28. When the crankshaft 26 isrotated in the rearward direction, the one-way clutch does not transmitrotational force from the crankshaft 26 to the front sprocket 28.Rotation of the crankshaft 26 in the forward direction refers torotation of the crankshaft 26 in the direction that moves the motorassist bicycle forward. The one-way clutch does not necessarily have tobe arranged between the crankshaft 26 and the front sprocket 28. Theomission of the one-way clutch allows for the operation of a coasterbrake arranged in the hub of the rear wheel 6.

A speed reduction mechanism and a transmission mechanism transmitrotational force from the motor 30 to the chain 22. The speed reductionmechanism uses a set of gears to reduce the speed of the rotationgenerated by the output shaft of the motor 30 and transmit the rotationto the transmission mechanism. The transmission mechanism may be asprocket that is engaged with the chain 22 or a gear mechanism thattransmits rotational force to the crankshaft 26.

FIG. 2 is a block diagram of the bicycle control device.

The bicycle control device includes a controller 32 and an input unit 34(refer to FIG. 3). The input unit 34 provides the controller 32 with asignal when operated by the rider. The controller 32 is arranged in, forexample, the crank unit 20. The controller 32 may include amicrocomputer, a memory, and an inverter that drives the motor 30.Preferably, the memory includes a non-volatile memory.

The controller 32 is connected to the motor 30, a cadence sensor 36, atorque sensor 38, a speed sensor 40, the operation unit 16, and thedisplay 18.

The cadence sensor 36, which is located in the crank unit 20, detectsthe rotation speed of the crankshaft 26 (number of rotations per minute,referred to as “the cadence” hereafter). The cadence sensor 36 may be,for example, a sensor that detects a magnet coupled to the crank arm.

The torque sensor 38 is located on the crank unit 20. A powertransmission member that transmits rotational force from the crankshaft26 to the front sprocket 28 is arranged in a transmission path betweenthe crankshaft 26 and the front sprocket 28. The torque sensor 38detects the actual torque generated at the power transmission member.Torque is related to the depression force (manual driving force) appliedto the pedals of the motor assist bicycle.

The speed sensor 40 is located on a chain stay of the frame 2 anddetects the rotation speed of the rear wheel 6. The speed sensor 40 maybe, for example, a sensor that detects a magnet coupled to the wheel.

The speed sensor 40 may be configured to detect the rotation speed ofthe front wheel 4.

The controller 32 receives signals from the cadence sensor 36 tocalculate the cadence. The calculated cadence may be shown on thedisplay 18.

The controller 32 receives signals from the torque sensor 38 tocalculate the torque. Further, the controller 32 receives signals fromthe speed sensor 40 to calculate the speed of the motor assist bicycle.The calculated bicycle speed may be shown on the display 18.

The controller 32 sets an assist force based on the bicycle speed andthe torque and controls the motor 30 to generate torque corresponding tothe assist force. The assist force is set based on a map, which isstored in advance.

The map indicates assist ratios in correspondence with bicycle speeds.The assist ratio shows the ratio of the assist force of the motor 30relative to manual driving force. Such a map is set for each operationmode of the motor 30. The controller 32 may use an equation instead of amap to set the assist force. The operation modes of the motor 30 willnow be described.

Description of Operation Modes

The controller 32 controls the motor 30 in a number of operation modes,which are classified into a number of ride modes and a walk mode. Theride modes are operation modes of the motor 30 when a rider rides themotor assist bicycle (hereinafter referred to as “the riding state”).More specifically, in the ride modes, the controller 32 drives the motor30 in correspondence with the manual driving force. The walk mode is anoperation mode of the motor 30 when the rider walks the motor assistbicycle (hereinafter referred to as “the walking state”). Morespecifically, in the walk mode, the controller 32 drives or stops themotor 30 in accordance with the operation of the input unit 34.

The ride modes include a normal mode and an off mode. In the normalmode, the motor 30 is driven. In the off mode, the motor 30 is notdriven.

The ride modes also include a number of modes that generate differentassist forces relative to the manual driving force. Preferably, the ridemodes include a high mode and an economic (eco) mode. The high mode isan operation mode that generates a larger assist force than the normalmode when in a predetermined bicycle speed range. The eco mode is anoperation mode that generates a smaller assist force than the normalmode when in a predetermined bicycle speed range. The walk mode is anoperation mode that allows the motor 30 to be driven when in a walkingspeed range. In the walk mode, speed restriction control is performed.When the speed restriction control is performed while the motor 30 isbeing driven in the walk mode, the controller 32 stops driving the motor30 if the bicycle speed becomes higher than or equal to a predeterminedvalue. This keeps the bicycle speed lower than a predetermined value.The predetermined value is, for example, equal to the value that stopsdriving the motor 30. This limits the bicycle speed at the predeterminedvalue.

Preferably, “the predetermined value” (upper limit value) is variable sothat the motor assist bicycle can be used by different riders who walkat different speeds. A switch used to set the predetermined value islocated on, for example, the operation unit 16. The predetermined valueis selected, for example, from three to five km/h.

In the walk mode, a torque restriction control is performed. When thetorque restriction control is performed while the motor 30 is driven inthe walk mode, the controller 32 stops driving the motor 30 if thetorque (manual driving force) becomes higher than or equal to apredetermined value. Thus, the motor 30 is not driven when the rider ispedaling.

FIG. 3 illustrates the display 18. The display 18 shows the operationmodes of the motor 30. As shown in FIG. 3, the display 18 is located,for example, near a left grip 10 a of the handle 10. The display 18includes first to fifth lamps 52, 54, 56, 58, 60. The first lamp 52 isilluminated when the operation mode is the high mode. The second lamp 54is illuminated when the operation mode is the normal mode. The thirdlamp 56 is illuminated when the operation mode is the eco mode. Thefourth lamp 58 is illuminated when the operation mode is the off mode.The fifth lamp 60 is illuminated when the operation mode is the walkmode. The display 18 may be configured by, for example, an LED displayor a liquid crystal display. When the display 18 is configured by aliquid crystal display, characters corresponding to the operation modesare shown instead of the first to fifth lamps 52, 54, 56, 58, and 60. Inthis case, the display 18 may show only characters indicating theselected operation mode. Alternatively, the display 18 may showcharacters indicating the selected operation mode differently fromcharacters indicating the other operation modes.

Switching of Operation Modes

FIG. 3 shows the operation unit 16. The operation mode of the motor 30is switched by operating the input unit 34. The operation unit 16 islocated near a grip. In the present embodiment, the operation unit 16 islocated near the left grip 10 a and the display 18, that is, between thedisplay 18 and the left grip 10 a. The operation unit 16 includes twoswitches, which configure the input unit 34. The switches may be, forexample, push button switches, touch switches, slide switches, or thelike. In the present embodiment, the input unit 34 includes a firstoperation switch 42 and a second operation switch 44. When the operationunit 16 is attached to the handle 10, the first operation switch 42 islocated below the second operation switch 44.

The first operation switch 42 and the second operation switch 44 eachsend an operation signal to the controller 32 when operated. The firstoperation switch 42 and the second operation switch 44 each output anoperation signal whenever pushed. The controller 32 receives operationsignals from the first operation switch 42 and operation signals fromthe second operation switch 44 and switches operation modes of the motor30 based on the operation signals.

When the controller 32 receives an operation signal from the firstoperation switch 42 in a ride mode (high mode or normal mode or ecomode), the controller 32 basically switches the operation mode to onethat decreases the assist force.

When the controller 32 receives an operation signal from the secondoperation switch 44 in a ride mode (normal mode or eco mode or offmode), the controller 32 basically switches the operation mode to onethat increases the assist force.

When a predetermined switch operation is performed in a ride mode, thecontroller 32 switches the operation mode from the ride mode to the walkmode. The processing of mode switching will now be described.

FIGS. 4 and 5 are flowcharts showing one example for processing modeswitching. The flowchart of FIG. 5 continues from the flowchart of FIG.4. The encircled character A in FIG. 4 is continuous with the encircledcharacter A in FIG. 5.

FIG. 4 shows the processes the controller 32 performs when the firstoperation switch 42 is pushed, and FIG. 5 shows the processes thecontroller 32 performs when the second operation switch 44 is pushed.When processing mode switching, the controller 32 first performs variousoperations based on the pushed state of the first operation switch 42and then performs various processes based on the pushed state of thesecond operation switch. The controller 32 repeats the mode switchingprocessing in predetermined cycles.

The processes performed when the first operation switch 42 is pushed(steps S11 to S19) will now be described with reference to FIG. 4. Instep S11, the controller 32 reads the pushed state of the firstoperation switch 42 and the pushed state of the second operation switch44. For example, when receiving an operation signal (signal indicatingpushed state) from the first operation switch 42, the controller 32determines that the first operation switch 42 is in a pushed state. Whenan operation signal is not received from the first operation switch 42,the controller 32 determines that the first operation switch 42 is notin a pushed state. When receiving an operation signal (signal indicatingpushed state) from the second operation switch 44, the controller 32determines that the second operation switch 44 is in a pushed state.When an operation signal is not received from the second operationswitch 44, the controller 32 determines that the second operation switch44 is not in a pushed state.

In step S12, the controller 32 determines whether or not the firstoperation switch 42 is in a pushed state. When determining that thefirst operation switch 42 is in the pushed state (YES), the controller32 proceeds to step S13. When determining that the first operationswitch 42 is not in the pushed state (NO), the controller 32 proceeds tostep S21 to perform processes related to the second operation switch 44.

In step S13, the controller 32 reads the state of the first operationswitch 42 in the previous cycle and determines whether or not the firstoperation switch 42 was in a pushed state. If the first operation switch42 was not in a pushed state in the previous cycle (NO), the controller32 proceeds to step S14. If the first operation switch 42 was in apushed state in the previous cycle (YES), the controller 32 proceeds tostep S21 to perform processes related to the second operation switch 44.

In steps S11 to S13, the controller 32 determines whether or not thefirst operation switch 42 that was not operated has now been operated.When the first operation switch 42 that was not operated has beenoperated, the controller 32 switches the operation mode throughsubsequent processes.

In step S14, the controller 32 determines whether or not the operationmode is a ride mode. When determining that the operation mode is a ridemode (YES), the controller 32 proceeds to step S15. When determiningthat the operation mode is not a ride mode, that is, the operation modeis the walk mode (NO), the controller 32 proceeds to step S18.

In step S15, the controller 32 determines whether or not the operationmode is in the off mode. When determining that the operation mode is oneother than the off mode (NO), the controller 32 proceeds to step S16.When determining that the operation mode is the off mode in step S15(YES), the controller 32 proceeds to step S17.

In step S16, the controller 32 basically switches the operation mode toone that decreases the assist force. For example, when the operationmode is the high mode, the controller 32 switches the operation mode tothe normal mode. When the operation mode is the normal mode, thecontroller 32 switches the operation mode to the eco mode. When theoperation mode is the eco mode, the controller 32 switches the operationmode to the off mode.

In step S17, the controller 32 switches the operation mode from the offmode to a walk mode standby condition. When in a walk mode standbycondition, the controller 32 waits for a command that drives the motor30 in the walk mode. Thus, the motor 30 is stopped in step S17.

In step S18, the controller 32 determines whether or not the motor 30 isbeing driven in the walk mode. In the walk mode, the motor 30 is in adrive condition, in which the controller 32 is driving the motor 30, ora standby condition, in which the controller 32 is waiting for a commandto drive the motor 30. In step S18, the controller 32 determines whichone of these conditions the controller 32 is in.

When the controller 32 is not driving the motor 30 in the walk mode(NO), the controller 32 proceeds to step S19 and drives the motor 30 inthe walk mode. When the controller 32 is driving the motor 30 in thewalk mode (YES), the controller 32 proceeds to step S21 to performprocesses related to the second operation switch 44.

The processes of steps S14 to S19 leads to the following results. If theoperation mode is a ride mode other than the off mode, the controller 32switches the operation mode to one that decreases the assist force whenthe first operation switch 42 is pushed. If the operation mode is theoff mode, the controller 32 switches the operation mode from the offmode to the walk mode when the first operation switch 42 is pushed. Whenswitching to the walk mode, the controller 32 does not drive the motor30. Rather, the controller 32 is in a standby condition and waits forthe next command. If the operation mode is the walk mode and the motor30 is stopped, the controller 32 drives the motor 30 when the firstoperation switch 42 is pushed. If the operation mode is the walk modeand the motor 30 is being driven, the controller 32 does not change theoperation mode of the motor 30 when the first operation switch 42 ispushed. If the operation mode is the walk mode and the motor 30 is beingdriven, the controller 32 continues to drive the motor 30 withoutchanging the operation mode as long as the first operation switch 42 andthe second operation switch 44 are both not pushed.

Processes based on the state of the second operation switch 44 (stepsS21 to S29) will now be described with reference to FIG. 5. In step S21,the controller 32 determines whether or not the second operation switch44 is in the pushed state. When determining that the second operationswitch 44 is in the pushed state (YES), the controller 32 proceeds tostep S22. When determining that the second operation switch 44 is not inthe pushed state (NO), the controller 32 proceeds to step S29. In stepS29, the controller 32 stores the state of the second operation switch44 in a memory. When the processing of mode switching is performed thenext time, the state of each switch stored in step S29 is read as theswitch state of the previous cycle.

In step S22, the controller 32 reads the state of the second operationswitch 44 in the previous cycle from the memory and determines whetheror not the second operation switch 44 was in a pushed state. If thesecond operation switch 44 was not in a pushed state in the previouscycle (NO), the controller 32 proceeds to step S23. If the secondoperation switch 44 was in a pushed state in the previous cycle (YES),the controller 32 proceeds to step S29.

In steps S21 and S22, the controller 32 determines whether or not thesecond operation switch 44 that was not operated has now been operated.When the second operation switch 44 that was not operated has beenoperated, the controller 32 switches the operation mode throughsubsequent processes (steps S23 to S26 and S28).

In step S23, the controller 32 determines whether or not the operationmode is a ride mode. When determining that the operation mode is a ridemode (YES), the controller 32 proceeds to step S24. When determiningthat the operation mode is not a ride mode, that is, the operation modeis the walk mode (NO), the controller 32 proceeds to step S26.

In step S24, the controller 32 determines whether or not the operationmode is the high mode. When determining that the operation mode is oneother than the high mode (NO), the controller 32 proceeds to step S25.When determining that the operation mode is the high mode in step S24(YES), the controller 32 proceeds to step S29.

In step S25, the controller 32 switches the operation mode to one thatincreases the assist force. For example, when the operation mode is theoff mode, the controller 32 switches the operation mode to the eco mode.When the operation mode is the eco mode, the controller 32 switches theoperation mode to the normal mode. When the operation mode is the normalmode, the controller 32 switches the operation mode to the high mode.

In step S26, the controller 32 determines whether or not the motor 30 isbeing driven in the walk mode. In the walk mode, the motor 30 is in adrive condition, in which the controller 32 is driving the motor 30, ora standby condition, in which the controller 32 is waiting for a commandto drive the motor 30. In step S26, the controller 32 determines whichone of these conditions the controller 32 is in. When the controller 32is driving the motor 30 in the walk mode (YES), the controller 32proceeds to step S27 and stops driving the motor 30. When the motor 30is not driven in the walk mode (NO), the controller 32 proceeds to stepS28 and switches the operation mode to the off mode.

The processes of steps S23 to S28 leads to the following results. If theoperation mode is the high mode, the controller 32 does not change theoperation mode of the motor 30 when the second operation switch 44 ispushed. If the operation mode is a ride mode other than the high mode,the controller 32 switches the operation mode to one that increases theassist force when the second operation switch 44 is pushed. If theoperation mode is the walk mode and the motor 30 is being driven, thecontroller 32 stops driving the motor 30 when the second operationswitch 44 is pushed. If the operation mode is the walk mode and themotor 30 is not being driven, the controller 32 switches the operationfrom the walk mode to the off mode.

The bicycle control device and the motor assist bicycle have theadvantages described below in the present embodiment.

When switched to the walk mode, the controller 32 drives and stops themotor 30 in accordance with the operation of the input unit 34. Thus,when the rider walks the bicycle, the driving of the wheel is assistedas intended by the rider.

In the walk mode, the motor 30 is not driven unless the first operationswitch 42 is operated twice. Thus, even if the operation mode isswitched from the ride mode to the walk mode, the motor 30 is not drivenimmediately. Once the driving of the motor 30 starts in the walk mode,the motor 30 is continuously driven without the need to keep pushing thefirst operation switch 42.

A single switch has two operation functions. That is, the firstoperation switch 42 has a function for switching ride modes and afunction for driving the motor 30 in the walk mode. This decreases thenumber of components in the operation unit 16 as compared with when aswitch is provided for each function.

When the speed of the motor assist bicycle becomes higher than or equalto the predetermined value (upper limit value) in the walk mode, thecontroller 32 stops driving the motor 30. This limits the speed of themotor assist bicycle so that the bicycle speed does not exceed thewalking speed of the rider.

Second Embodiment

The controller 32 in a further embodiment will now be described withreference to FIG. 6. In the present embodiment, the controller 32 hasthe same configuration as the controller 32 of the first embodiment. Inthe description hereafter, same reference numerals are given to thosecomponents that are the same as the corresponding components of thefirst embodiment.

The controller 32 of the present embodiment differs from the controller32 of the first embodiment in the processing of mode switching. Inparticular, the processes related with the first operation switch 42differ from the first embodiment. The processes related with the secondoperation switch 44 are the same as the first embodiment and thus willnot be described below. The encircled characters A in FIG. 6 arecontinuous with the encircled character A in FIG. 5. The processesrelated with the first operation switch 42 will now be described.

The controller 32 of the present embodiment performs the same processesas the first embodiment when the first operation switch 42 was in apushed state in the previous cycle and is in a pushed state in thepresent cycle. More specifically, steps S31 to S39 in FIG. 6 of thepresent embodiment are the same as steps S11 to S19 of the firstembodiment. Thus, steps S31 to S39 will not be described below. When thefirst operation switch 42 is not in a pushed state in the present cycle,predetermined processes are performed based on the state of the switch42 in the present cycle. This differs from the first embodiment.

In step S32, when determining that the first operation switch 42 is notin a pushed state, the controller 32 proceeds to step S41.

In step S41, the controller 32 reads the state of the first operationswitch 42 in the previous cycle and determines whether or not the firstoperation switch 42 was in a pushed state in the previous cycle. Whenthe first operation switch 42 was not in the pushed state in theprevious cycle (NO), the controller 32 proceeds to step S21. When thefirst operation switch 42 was in the pushed state in the previous cycle(YES), the controller 32 proceeds to step S42 and determines whether ornot the motor 30 is being driven in the walk mode.

When the controller 32 is not driving the motor 30 in the walk mode(NO), the controller 32 proceeds to step S21 and performs processesrelated with the second operation switch 44. When the controller 32 isdriving the motor 30 in the walk mode (YES), the controller 32 proceedsto step S43 and stops driving the motor 30.

The processes of steps S41 to S43 leads to the following results. If theoperation mode is the walk mode and the motor 30 is being driven, thecontroller 32 stops driving the motor 30 when the pushed first operationswitch 42 is released, that is, when the operated first operation switch42 is no longer operated. If the operation mode is the walk mode and themotor 30 is being driven, the controller 32 does not change theoperation mode as long as the first operation switch 42 remains pushed(YES in step S33). In this manner, the drive state of the motor 30 ismaintained by continuously pushing the first operation switch 42.

In the present embodiment, the motor 30 remains driven in the walk modeby keeping the first operation switch 42 in the pushed state. When thefirst operation switch 42 is released from the pushed state, the motor30 is no longer driven in the walk mode.

The advantages of the bicycle control device in the present embodimentwill now be described.

The assistance provided by the motor 30 may be cancelled just bystopping the operation of the first operation switch 42.

Third Embodiment

The operation unit 16 and the display 18 in a further embodiment willnow be described with reference to FIG. 7. In the present embodiment,components of the operation unit 16 and the display 18 that have thesame configuration as the first embodiment will not be described. In thefirst embodiment, the input unit 34 is independent from other devices,whereas in the present embodiment, a gearshift operation unit 62includes functions of the operation unit 16 serving as the input unit34.

The operation unit 16 includes the second operation switch 44 and thefirst operation switch 42, which form the input unit 34. The secondoperation switch 44 and the first operation switch 42 have the samefunctions as the second operation switch 44 and the first operationswitch 42 of the first embodiment. Although the second operation switch44 and the first operation switch 42 allow operation modes to bechanged, the second operation switch 44 and the first operation switch42 cannot be used to drive and stop the motor 30.

The gearshift operation unit 62 includes a gearshift switch 66 and athird operation switch 68. The gearshift switch 66 is used to change thegear ratio in a derailleur of the bicycle. The gearshift operation unit62 includes a display 64 that shows a gear number, which corresponds tothe gear ratio of the derailleur. The third operation switch 68 islocated near the gearshift operation unit 62. Preferably, the thirdoperation switch 68 is arranged within a range reached by the thumb ofthe rider when the rider is gripping the grip of the handle 10. Thisallows the rider to operate the third operation switch 68 while grippingthe grip. In the present embodiment, the gearshift operation unit 62 isattached to the handle 10 near a right grip 10 b.

The third operation switch 68 is a switch used to drive and stop themotor 30 in the walk mode. The controller 32 receives an operationsignal from the third operation switch 68 during only the off mode andthe walk mode. The controller 32 acknowledges the operation of the thirdoperation switch 68 as being the same as the operation of the firstoperation switch 42. Thus, the controller 32 performs a processcorresponding to the operation of the first operation switch 42 whenprocessing mode switching. For example, the third operation switch 68performs mode switching processing in the same manner as the first andsecond embodiments when the third operation switch 68 is operated.

If the operation mode is the off mode, the controller 32 switches theoperation mode to the walk mode when the third operation switch 68 ispushed. In this case, the controller 32 enters a standby state and waitsfor the next command without driving the motor 30. If the operation modeis the walk mode and the motor 30 is stopped, the controller 32 drivesthe motor 30 when the third operation switch 68 is pushed. If theoperation mode is the walk mode and the motor 30 is being driven, thecontroller 32 stops driving the motor 30 when the pushed third operationswitch 68 is released.

If the third operation switch 68 is continuously pushed when theoperation mode is the walk mode and the motor 30 is being driven, thecontroller 32 does not change the operation mode. In this manner, thedrive state of the motor 30 is maintained by continuously pushing thethird operation switch 68.

The controller 32 permits or restricts the shifting of gears with thegearshift switch 66 depending on the operation mode. For example, whenin a ride mode, the controller 32 permits the shifting of gears with thegearshift switch 66. When in the walk mode, the controller 32 prohibitsthe shifting of gears with the gearshift switch 66. Since gears cannotbe changed when the rider is walking the bicycle, sudden changes in thebicycle speed are limited.

In the present embodiment, the switch for changing the operation mode isarranged independently from the switch for driving the motor 30 in thewalk mode. This allows the switch for driving the motor 30 in the walkmode to be located at a position where the switch can easily be operatedwhen walking the bicycle.

In the first and second embodiments, if the operation mode is the offmode when the first operation switch 42 is operated, the controller 32switches the operation mode to the walk mode (step S15 and step S35).The operation mode may be switched to the walk mode when certainconditions are satisfied. For example, when the operation mode is theoff mode, the controller 32 switches the operation mode to the walk modewhen the first operation switch 42 is pushed over a predetermined timeor longer. This limits switching of the operation mode from the off modeto the off mode when the rider does not intend to do so.

Preferably, in the first embodiment and the second embodiment, thebicycle control device is configured as described below. When the poweris turned off in the walk mode and subsequently turned on, thecontroller 32 controls the motor 30 to be in a ride mode (e.g., normalmode or off mode). Alternatively, regardless of the operation mode whenthe power is turned off, the controller 32 may control the motor 30 tobe in a ride mode (e.g., normal mode or off mode) when the power issubsequently turned on. In this case, when the power is turned on to usethe motor assist bicycle, the operation mode is always in a ride mode.This allows the rider to always use the motor assist bicycle in the ridemode when commencing use of the bicycle.

Preferably, in each of the above embodiments, the controller 32gradually raises a torque command value that is used to drive the motor30 when starting the driving of the motor 30 based on the firstoperation switch 42 or the third operation switch 68 (refer to FIG. 8).The torque command value is, for example, a current value provided tothe motor 30. This allows the bicycle to start moving smoothly whendriving the motor 30 in the walk mode. The time T1 until the torquecommand value output from the controller 32 becomes maximal is selectedfrom one to five seconds and is, for example, three seconds.

Preferably, in each of the above embodiments, when in the walk mode, thecontroller 32 controls the motor 30 so that the output torque of themotor 30 is less than or equal to a predetermined torque value Tm (referto FIG. 8). The predetermined torque value Tm is selected to limitincreases in the speed of the bicycle when, for example, walking thebicycle uphill. This restricts the output torque of the motor 30 evenwhen the speed does not reach a predetermined speed. As a result, thespeed of the bicycle is limited, which is driven by the motor 30.

Preferably, in each of the above embodiments, when stopping the motor 30based on the first operation switch 42 or the third operation switch 68,the controller 32 gradually decreases the torque command value used todrive the motor 30 (refer to FIG. 8). The torque command value is, forexample, a current value. The time T2 until the torque command valueoutput from the controller 32 becomes minimal (0) is selected from fiftymilliseconds to one second. This limits reverse rotation of thecrankshaft 26 when driving or stopping the motor 30 in the walk mode.

Preferably, in each of the above embodiments, the controller 32 stopsdriving the motor 30 if the rotation speed of the wheel becomes lessthan or equal to a predetermined value when the motor 30 is driven inthe walk mode. The predetermined value is, for example, zero. When, forexample, applying the brakes of the bicycle, the rotation speed of thewheel decreases even when the motor 30 is driven. Accordingly, even whenassisted by the motor 30 while walking the bicycle, the motor 30 caneasily be stopped when applying the brakes of the bicycle. When thepredetermined value is a value that is greater than zero, the controller32 controls the motor 30 to gradually decrease the output of the motor30 when stopping the motor 30.

Preferably, in each of the above embodiments, if load that is greaterthan a predetermined value acts on the motor 30 when the motor is drivenin the walk mode, the controller 32 forcibly stops the motor 30.Preferably, the controller 32 gradually decreases the torque commandvalue used to drive the motor 30 when stopping the motor 30 (refer toFIG. 9). The time until the torque command value output from thecontroller 32 becomes minimal (0) is selected from one to twentyseconds. The selected time is, for example, five seconds. This allowsthe rider to recognize a decrease in the assist force and cope with sucha situation even if the motor 30 is stopped when walking the bicyclealong a road (e.g., steep uphill) that applies a high load to the motor30.

In the third embodiment, the third operation switch 68 is located nearthe right grip 10 b of the handle 10 but may be located near the leftgrip 10 a.

In each of the above embodiments, the displays 18 and 64 may be separatefrom the operation unit 16. In this case, the displays 18 and 64 may belocated, for example, at the middle portion of the handle 10.

In each of the above embodiments, the display state of the displays 18and 64 when the motor 30 is stopped in the walk mode may be changed fromthat when the motor 30 is driven. For example, the fifth lamp 60 iscontinuously illuminated when the motor 30 is stopped, and the fifthlamp 60 is intermittently illuminated when the motor 30 is driven.Alternatively, the color of the fifth lamp 60 may be changed. If thedisplays 18 and 64 are formed by liquid crystal displays, the displayedcharacters when the motor 30 is stopped may be changed from thedisplayed characters when the motor 30 is driven.

The microcomputer of the controller 32 is one example of a computerprocessor configured to execute control program(s) or control method(s)as illustrated in the drawings. The memory of the controller 32 is oneexample of a non-transitory computer-readable recording medium havingstored thereon, a program or computer-executable instructions. Suchcomputer-readable recording medium can be any available media that canbe accessed by a general purpose or special purpose computer such as thecomputer processor of the controller 32. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium which can be used to carryor store desired program code means in the form of computer-executableinstructions or data structures and which can be accessed by a generalpurpose or special purpose computer.

It should be apparent to those skilled in the art that the presentinvention may be embodied in many other specific forms without departingfrom the scope of the invention. Therefore, the present examples andembodiments are to be considered as illustrative and not restrictive,and the invention is not to be limited to the details given herein, butmay be modified within the scope and equivalence of the appended claims.

1-20. (canceled)
 21. A bicycle control device that controls a motor toassist driving of a wheel of a bicycle, the bicycle control devicecomprising: a controller configured to control the motor; and anoperation unit configured to be operated to switch operation modes ofthe motor, wherein the controller includes at least a walk mode as theoperation modes, and in a case that a rotation speed of a wheel becomeslower than or equal to a predetermined value while the motor is drivenin the walk mode, the controller is configured to control the motor soas to gradually decrease output of the motor and then stop driving themotor.
 22. A bicycle control device that controls a motor to assistdriving of a wheel of a bicycle, the bicycle control device comprising:a controller configured to control the motor; and an operation unitconfigured to be operated to switch operation modes of the motor,wherein the controller includes at least a walk mode as the operationmodes, and in a case that load that is equal to or greater than apredetermined value acts on the motor while the motor is driven in thewalk mode, the controller is configured to control the motor so as togradually decrease output of the motor and then stop driving the motor.23. A bicycle control device that controls a motor to assist driving ofa wheel of a bicycle, the bicycle control device comprising: acontroller configured to control the motor; and an operation unitconfigured to be operated to switch operation modes of the motor and tostop the motor, wherein the controller includes at least a walk mode asthe operation modes, and in a case that the controller is controllingthe motor to stop driving the motor in correspondence with the operationof the input unit while the motor is driven in the walk mode, thecontroller is configured, after the operation unit is operated, tocontrol the motor so as to gradually decrease output of the motor andthen stop driving the motor.
 24. The bicycle control device according toclaim 23, wherein the controller is configured to drive the motor onlywhile the operation unit is continuously operated in the walk mode.